A laparoscopic surgery is applied more and more widely. In order to avoid iatrogenic infection, the consumption of a disposable trocar used in the laparoscopic surgery is increasingly greater. The trend of simplifying the structure, reducing the cost and improving the performance on the basis of ensuring the using performance has already become an improvement direction of the trocar.
In order to facilitate the surgery, it is required that the trocar can both use a 5 mm surgical instrument, and a 10 mm or 12 mm surgical instrument. Therefore, a diameter of an instrument through hole of a radial sealing ring of the trocar is generally smaller than 4 mm. When a surgical instrument with a relatively large diameter such as 10mm or 12 mm passes through the 4 mm surgical instrument through hole of the radial sealing ring, the radial sealing ring generates a relatively large surrounding force, when the surgical instrument moves back and forth, an upper pressing plate of a radial sealing ring assembly may hit against an upper cover, or a lower pressing plate of the radial sealing ring assembly may hit against a lower cover to produce an impact sound, thereby forming noise interfering a doctor. Due to the defects of the impact sound produced when the surgical instrument moves back and forth, the trocar in the prior art needs to be improved.